The present disclosure provides an optical compensation film, a photomask, and an exposure apparatus. The optical compensation film includes a first region of the optical compensation film and a second region of the optical compensation film. The first region of the optical compensation film is positioned to correspond to an overlapping portion of the prisms, and is configured to allow light to pass therethrough and impinge on the overlapping portion of the prisms. The second region of the optical compensation film is positioned to correspond to a non-overlapping portion of the prisms, and is configured to allow light to pass therethrough and impinge on the non-overlapping portion of the prisms. Light transmittance of the first region of the optical compensation film is greater than light transmittance of the second region of the optical compensation film.